While the origin of the bicycle dates as far back as the mid-17th century, when wheeled vehicles were moved by the action of pushing on the ground with one's feet, the real technical innovation in this domain came in the early 19th century with the invention of swinging pedal cranks for two wheeled vehicles. At that time, swinging pedal cranks were placed on either side of the front wheel of the bicycle which transmitted a movement to the rear wheel by means of two light connecting rods. This invention was not very successful because the pedals did not rotate, but rather followed circular arcs which caused rider fatigue in the knee joints. The invention which really advanced the innovation of the bicycle came in the mid 1800s when pedal cranks were made to pivot integrally around the axle of the front wheel, to which the pedals transmitted their movement directly. This invention was known as the velocipede. Later that century, spoked wheels and metal frames were designed which made the vehicle appreciably lighter, as well as the incorporation of an endless drive chain to transmit energy directly to the rear wheel.
Bicycles have long been used as a means for both transportation and recreation. In fact, in some countries throughout the world the bicycle is the primary mode of transportation, replacing automobiles, trains, buses, etc. Prior art bicycles abound with design variations concerning primarily size, weight, appearance, flexibility and reliability. There are various types and configurations of bicycles available, the two most popular of which are the mountainbike and the twenty-one speed, or racing, bike. Regardless of its type, the conventional bicycle is generally characterized by a frame which rotatably supports a plurality of wheels, a steering mechanism mounted to the frame for controlling movement of the wheels, a drive assembly interconnected between the frame and the wheels for imparting rotary movement to the wheels, and a seat upon which the user is supported for transport.
Recent innovations in the evolution of the bicycle have involved improving its shock absorption characteristics. This is particularly true for mountain-bikes which are especially designed to be ridden over rugged terrain. Due to their relatively rigid frames, bicycles transmit shocks resulting from bumps, pot holes, rocks or other discontinuities in the riding surface directly to the rider. Such surface discontinuities, over prolonged period of riding time, can result in discomfort to the rider and increased fatigue as the rider attempts to reposition himself/herself on the bicycle in anticipation of upcoming obstacles.
In an effort to provide a more comfortable environment for the rider, manufacturers have designed various types of shock absorption systems for use primarily with the front and rear wheels of the bicycle. Much like the suspension systems associated with automobiles, bicycle shock absorbers allow the rider to travel smoothly over the rugged terrain. While the bicycle's wheels may jolt up and down, springs between the wheels and the bicycle frame flex and absorb the force of these jolts. This ensures that the force of the bumping is not transferred to the rider. Springs alone tend to produce a bouncing motion, so the suspension system may also incorporate dampers, which slow the movement of the springs to prevent the bicycle and its rider from bouncing up and down.
It is also known to incorporate shock absorbers in other areas of the bicycle frame. For example, U.S. Pat. No. 5,217,241, issued Jun. 8, 1993, relates to such a suspension system which is capable of transforming pedal force into forward motive force when in high gears, while providing increased traction in the lower gears. Here, the shock absorber system comprises a pair of tubular chain stays disposed on either side of the bicycle's rear wheel, first ends of which pivot relative to the frame's seat tube, and second ends of which are joined to a seat stay. Disposed on the seat stay is a displacable spring assembly secured to the upper portion of the seat tube. As the bicycle frame experiences a load while the rear wheel remains affixed against the ground, the chain stays are urged to rotate upwardly about their pivot point. The load force and resulting displacement are transferred directly from the rear axle through the seat stays to the spring assembly.
While the forgoing bicycle shock absorption systems are useful in their own right, there remains a need to provide a new and improved shock absorber for bicycles, or other types of cycles, for cushioning impact in the seated region. It would be desirable for such a shock absorber to be adjustable so that absorption characteristics can be selectively varied with little difficulty by the rider. It would further be desirable for such a shock absorber to be substantially concealed from view within the frame of the cycle so that the cycle is both aesthetically pleasing, yet still able to accommodate various accessories frequently mounted to the bicycle frame. The present invention is directed to meeting these needs, among others.